Write pole fabricated using a carbon hard mask and method of making

ABSTRACT

A magnetic writer comprises a write pole, a substrate and a non-magnetic, oxygen-free buffer material. The write pole has a leading edge, a trailing edge, a first side and second side. The substrate is at the leading edge of the write pole. The non-magnetic, oxygen-free buffer material is located between the write pole and the substrate.

BACKGROUND

Magnetic transducing heads typically include both a write element and aread element. The write element is configured to generate magneticfields that align magnetic moments of the recording data to representbits of data.

To write data to a recording medium, an electric current can be appliedto conductive coils to induce a magnetic field in the medium under awrite pole. The write pole can define the track width of the datawritten. More specifically, in perpendicular recording the magneticsignals can be conducted through the trailing edge of the write pole ina manner that orients the magnetic moments of the recording mediumperpendicularly to the surface of the recording medium. The shape of thewrite pole may be projected and reproduced on the magnetic medium duringthe write process. Thus, the track width can be defined by the width ofthe write pole at the surface facing the recording medium (i.e. airbearing surface).

One way to increase the recording capacity of medium is to decrease thewidth of the write pole. Sub-100 nm features (write poles having a widthof less than 100 nm) can enable this increase in capacity. A write polecan be fabricated by depositing magnetic material, a hard mask and aphotoresist patterning mask on a substrate. After deposition, thephotoresist is patterned by photolithography. The photoresist is used topattern the hard mask material using a material removal process such asreactive ion etching (RIE). Then, using the hard mask as a pattern,select portions of the magnetic material are removed by a millingprocess to form a write pole. Previously, hard masks were formed fromAl₂O₃, SiO₂, SiON, poly-Si and other similar materials. However, thesehard masks are not effective for the fabrication of sub-100 nm writepoles because in some cases the patterned hard masks of these materialsmust be thicker than 100 nm. That is, the required thickness of the hardmask was thicker than the width of the mask, resulting in decreasedstability of the hard mask. The materials of these hard masks alsosuffered from negative contamination issues, such as contamination fromoxygen ions. An improved method of forming features on magnetictransducing heads is necessary.

SUMMARY

A magnetic writer comprises a write pole, a substrate and anon-magnetic, oxygen-free buffer material. The write pole has a leadingedge, a trailing edge, a first side and second side. The substrate is atthe leading edge of the write pole. The non-magnetic, oxygen-free buffermaterial is located between the write pole and the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a recording head taken substantiallynormal to a magnetic medium.

FIG. 2 is an end view of a write pole having a non-magnetic, oxygen-freebuffer layer and steep sidewalls as viewed from the magnetic medium.

FIG. 3-FIG. 7 illustrate the process for forming the write pole having anon-magnetic, oxygen-free buffer layer and steep sidewalls as shown inFIG. 2.

FIG. 8 is a chart of the mill rate in angstroms per second of alumina,cobalt iron and amorphous carbon over a range of mill angles in degrees.

FIG. 9 is a cross-sectional view of a write pole having an aluminainsulating layer in place of the non-magnetic, oxygen-free buffer layerduring an argon ion milling process.

DETAILED DESCRIPTION

FIG. 1 is a cross-sectional view of recording head 10, which includesreader 12 and writer 14 that define medium confronting surface 16.Reader 12 and writer 14 each have medium confronting surface 16, leadingedge 18 and trailing edge 20. Reader 12 includes bottom shield structure22, read element 24, read gap 26, and top shield structure 28. Writer 14includes first return pole 30, first magnetic stud 32, write pole 34,second magnetic stud 36, second return pole 38, first conductive coil40, and second conductive coil 42. Write pole 34 includes yoke 44, writepole body 46 and write pole tip 48. Front shield 50 shields write pole34.

Reader 12 and writer 14 are multi-layered devices having features formedby layered materials. In one example, as illustrated in FIG. 1, writer14 is stacked on reader 12 in a piggyback configuration in which layersare not shared between the two elements. In other examples, reader 12and writer 14 can be arranged in a merged-head configuration (in whichlayers are shared between the two elements) and/or reader 12 may beformed on writer 14.

On reader 12, read gap 26 is defined on medium confronting surface 16between terminating ends of bottom shield 22 and top shield 28. Readelement 24 is positioned in read gap 26 adjacent medium confrontingsurface 16. Read element 24 may be any variety of different types ofread elements, such as a magnetoresistive (MR) element, a tunnelingmagnetoresistive (TMR) read element or a giant magnetoresistive (GMR)read element.

Recording head 10 confronts magnetic medium 60 at medium confrontingsurface 16, such as an air bearing surface (ABS). Reader 12 and writer14 are carried over the surface of magnetic medium 60, which is movedrelative to recording head 10 as indicated by arrow A such that writepole 34 trails first return pole 30 and leads second return pole 38.Writer 14 has leading edge 18 and trailing edge 20 defined by themovement of magnetic medium 60. Write pole 34 is used to physicallywrite data to magnetic medium 60. In order to write data to magneticmedium 60, current is caused to flow through second conductive coil 42.The magnetomotive force in the coils causes magnetic flux to travel fromwrite pole tip 48 perpendicularly through magnetic medium 60, andthrough second return pole 38 and second magnetic stud 36 to provide aclosed magnetic flux path. The direction of the write field at themedium confronting surface of write pole tip 48, which is related to thestate of the data written to magnetic medium 60, is controllable basedon the direction that the current flows through second conductive coil42.

Reader 12 reads data from magnetic medium 60. In operation, magneticflux from a surface of magnetic medium 60 causes rotation of amagnetization vector of read element 24, which in turn causes a changein electrical resistivity of read element 24. The change in resistivityof read element 24 can be detected by passing a current through readelement 24 and measuring a voltage across read element 24. Shields 22and 28, which may be made of a soft ferromagnetic material, guide straymagnetic flux from magnetic medium 60 away from read element 24 outsidethe area of magnetic medium 60 directly below read element 24.

In writer 14, first return pole 30, second return pole 38, firstmagnetic stud 32, and second magnetic stud 36 can comprise soft magneticmaterials, such as NiFe. Conductive coils 40 and 42 can comprise amaterial with low electrical resistance, such as Cu. Write pole body 44can comprise a high moment soft magnetic material, such as CoFe. Firstconductive coil 40 surrounds first magnetic stud 32, which magneticallycouples write pole 34 to first return pole 30. Second conductive coil 42surrounds second magnetic stud 36, which magnetically couples write pole34 to second return pole 38. First conductive coil 40 passes through thegap between first return pole 30 and write pole 34, and secondconductive coil 42 passes through the gap between write pole 34 andsecond return pole 38.

Magnetic medium 60 is shown merely for purposes of illustration, and maybe any type of medium that can be used in conjunction with recordinghead 10, such as composite media, continuous/granular coupled (CGC)media, discrete track media, and bit-patterned media.

Reader 12 and writer 14 are shown merely for purposes of illustrating aconstruction that may be used in a recording head 10 and variations onthe designs may be made. For example, a single trailing return pole maybe provided on writer 14 instead of the shown dual return pole writerconfiguration, or alternative coil 40, 42 designs can be used.

FIG. 2 is an end view of write pole 48 as seen from magnetic medium 60.Write pole 48 is formed on substrate 70 and oxygen-free buffer layer 72,and is surrounded by insulating layer 74. Chemical-mechanical polishing(CMP) stop layer 76 is formed on top of write pole. Write pole 48 hassidewalls 78, which form sidewall angles θ_(s) with the vertical axis.Substrate 70 can include any thin films of writer 14 or reader 12previously formed during upstream fabrication.

Oxygen-free buffer layer 72 is non-magnetic. In one example, oxygen-freebuffer layer 72 is a non-magnetic refractory metal or a non-magnetic,non-oxide nitride, carbide or boride or combinations thereof. In anotherexample, oxygen-free buffer layer 72 is selected from W, Cr, Mo, V, Nb,Ta, Hf, Zr, Ti, AlN, B₄C, TaC, TiN, TiB₂, WC, HfC, Cr₃C and combinationsthereof.

Write pole 48 is located adjacent oxygen-free buffer layer 72 on theopposite side of substrate 70. Write pole 48 comprises a magneticmaterial. For example, write pole 48 can be formed from a high Bsat orhigh moment soft magnetic material such as CoFe. As illustrated in FIG.2, write pole 48 can be fabricated to have a trapezoidal or taperedshape. This trapezoidal shape prevents adjacent track writing problemsassociated with skew, which occurs when write pole 48 is positioned atan angle relative to the medium and portions of write pole 48 areoutside of the desired track. The use of oxygen-free buffer layer 72 anda carbon hard mask during the fabrication of a trapezoidal shaped writepole 48 enables write pole 48 to be fabricated with a larger (orsteeper) sidewall angle θ_(s) as will be described later.

Insulating layer 74 is located on top of selected portions ofoxygen-free buffer layer 72. Insulating layer 74 surrounds and insulateswrite pole 48. Insulating layer 74 comprises a non-magnetic insulatingmaterial. In one example, insulating layer 74 comprises alumina.Insulating layer 74 has a level surface at trailing edge 20.

Finally, chemical-mechanical polishing (CMP) stop layer 76 is locatedadjacent write pole 48 on the opposite side of oxygen-free buffer layer72. CMP stop layer 76 comprises amorphous carbon (a-C). CMP stop layer76 functions as a stop layer during fabrication of the write element andassists in forming the level surface of insulating layer 74 at trailingedge 20.

FIGS. 3-7 are cross-sectional views of a substrate during fabrication ofwrite pole 48 and illustrate a method of making write pole 48 having alarge sidewall angle θ_(s) using a carbon hard mask. The steps includeforming a layered substrate or structure, patterning a cap layer,patterning a carbon hard mask, forming the write pole and backfillingthe substrate.

First, as illustrated in FIG. 3, layers are deposited on substrate 70 toform layered structure 79. With substrate 70 as a base, oxygen-freebuffer layer 72 is deposited, then write pole material 80, CMP stoplayer 76, hard mask 81 (including Al₂O₃ spacer layer 82, carbon hardmask 84 and cap layer 86) and photoresist mask 88.

Oxygen-free buffer layer 72 is a non-magnetic material. In one example,oxygen-free buffer layer 72 is a non-magnetic refractory metal or anon-magnetic, non-oxide nitride, carbide or boride or a combinationthereof. In another example, oxygen-free buffer layer 72 is selectedfrom W, Cr, Mo, V, Nb, Ta, Hf, Zr, Ti, AlN, B₄C, TaC, TiN, TiB₂, WC,HfC, Cr₃C and combinations thereof. Oxygen-free buffer layer 72 is athin layer. In one example, oxygen-free buffer layer 72 is about 3000angstroms thick. Oxygen-free buffer layer 72 does not adversely affectthe sidewall mill resistance of carbon hard mask 84, allowing write pole48 to be formed with larger sidewall angles.

Write pole material 80 is a high moment magnetic material that will beformed into write pole 48. In one example, write pole material 80 has amagnetic moment of at least 2.0 tesla (T). In another example, writepole material 80 has a magnetic moment of about 2.4 T. In a furtherexample, write pole material 80 includes at least one of CoFe, CoFeNi,CoFeRh, CoFeRu, CoFePt, CoFePd and NiFe. Write pole material 80 is athin layer. In one example, write pole material 80 is about 2000angstroms thick.

CMP stop layer 76 is layered on write pole material 80. CMP stop layer76 is formed from amorphous carbon (a-C). In one example, CMP stop layer76 is about 100 angstroms thick.

Hard mask 81 consisting of Al₂O₃ spacer layer 82, carbon hard mask 84and cap layer 86 is deposited on CMP stop layer 76. Carbon hard mask 84is formed from amorphous carbon (a-C) or diamond like carbon (DLC).Carbon hard mask 84 is used to pattern write pole material 80. In oneexample, carbon hard mask 84 is between about 4000 and 6000 angstromsthick. Carbon hard mask 84 can be deposited by magnetron sputteringtechniques, reactive magnetron sputtering techniques, plasma-enhancedchemical vapor deposition (PECVD) or ion beam deposition (IBD). In oneexample, carbon hard mask 84 is deposited by direct current (DC)magnetron sputtering of a graphite target in argon gas with a radiofrequency (RF) substrate bias. Specific features and characteristics ofcarbon hard mask 84 will be described later.

Cap layer 86 is formed from a material having a high etch selectivity tophotoresist 88. In one example, cap layer 86 is formed from a siliconbased material, such as silicon oxinitride (SiON), silicon nitride orsilicon oxide. Cap layer 86 can be deposited on carbon hard mask 84 byplasma-enhanced chemical vapor deposition (PECVD). Cap layer 86 canfunction as both an anti-reflective coating and an etch mask for carbonhard mask 84. In one example, cap layer 86 is between about 50 and about150 nm thick. Carbon hard mask 84 and photoresist 88 can be removedusing the same chemistry, while cap layer 86 is removed using adifferent chemistry. Therefore, cap layer 86 prevents undesirablyetching carbon hard mask 84 during the patterning of photoresist 88.Hard mask 81 can include additional layers above or below carbon hardmask 84. For example, hard mask 81 can include an additional layer toimprove adhesion of hard mask 81 to write pole material 80.

Photoresist 88 is deposited on top of cap layer 86. Photoresist 88 ispatterned using a photolithography process. Photolithography uses lightto transfer a pattern from a photomask to light sensitive photoresist88. Photoresist 88 in FIG. 3 has already been patterned to have widthdw₁.

With patterned photoresist 88 in place, cap layer 86 is etched andphotoresist 88 is removed as shown in FIG. 4. During the etching, anyportion of cap layer 86 not covered by photoresist 88 will be removed.Cap layer 86 can be etched using either reactive ion etching (RIE) orplasma etching. In one example, cap layer 86 is etched by RIE usingfluorinated chemistry, such as CF₄. After patterning, cap layer 86 haswidth d_(w2).

Next, carbon hard mask 84 is etched as shown in FIG. 5. Cap layer 86 isused as a pattern when etching carbon hard mask 84 so that portions ofcarbon hard mask 84 not covered by cap layer 86 are removed. Carbon hardmask 84 can be etched using reactive ion etching (RIE) or plasmaetching. In one example, carbon hard mask 84 is etched by RIE usingoxygen chemistry. The etching process is selected so that it does notremove CMP stop layer 76. After patterning, carbon hard mask 84 haswidth d_(w3).

Then, as shown in FIG. 6, CMP stop layer 76 and write pole material 80are milled to form trapezoidal write pole 48 with sidewalls 78. Carbonhard mask 84 is used as a pattern, and portions of write pole material80 and CMP stop layer 76 not covered by carbon hard mask 84 are removedby the milling process. The milling process will also remove cap layer86 and a portion of carbon hard mask 84. In one example, argon ionmilling is used. In argon ion milling, argon ions (illustrated by arrows90) are accelerated towards write pole material 80. Mill angle θ_(m) ofthe argon ions can be controlled during the milling process to controlthe shape of write pole 48. In one example, the argon ions strike CMPstop layer 76 and write pole material 80 nearly vertically (mill angleθ_(m) is small) until the majority of the write pole material isremoved. Then, mill angle θ_(m) is increased so that write pole material80 is milled slightly laterally, forming a trapezoidal or tapered writepole 48. The high mill resistivity (or low mill rate) of carbon hardmask 84 maintains the desired width of write pole material 80 attrailing edge 20 while sidewalls 78 can be etched to form a trapezoidalshape. After the milling process, carbon hard mask 84 and thus trailingedge 20 of write pole 48 has width d_(w4). As described further below,the combination of oxygen-free buffer layer 72 and carbon hard mask 84allow write pole 48 to be formed with steeper sidewalls 78 (sidewallangle θ_(s) is increased).

During the milling process, a portion of oxygen-free buffer layer 72 isremoved, as illustrated in FIG. 6. Oxygen-free buffer layer 72 is sizedso that a portion of oxygen-free buffer layer 72 can be removed duringthe milling process without exposing substrate 70. As discussed above,the milling process removes cap layer 86 and a portion of carbon hardmask 84. Following the milling process, spacer layer 82 and theremaining portion of carbon hard mask 84 can be removed. For example, anashing process using oxygen or hydrogen chemistry can be used to removespacer layer 82 and carbon hard mask 84.

After forming write pole 48 and removing spacer layer 82 and carbon hardmask 84, substrate 70 is backfilled with insulating layer 74, asillustrated in FIG. 7. Insulating layer 74 is deposited on oxygen-freebuffer layer 72, and surrounds and insulates write pole 48. In oneexample, insulating layer 74 is alumina (Al₂O₃) that is deposited by aphysical vapor deposition (PVD) process such as radio frequency (RF)reactive.

Backfilling results in an uneven surface at trailing edge 20.Chemical-mechanical planarization (CMP) is used to level trailing edgesurface 20. Insulating layer 74 is subjected to the CMP process untilCMP stop layer 76 is reached, forming the write element shown in FIG. 2.Downstream processing of the write element can include removing CMP stoplayer 76 such as by oxygen plasma, and the remaining features of thewriter can be manufactured by processes known in the art.

As discussed above, in order for the storage capacity of medium to beincreased, the width of writer 14, and specifically of write pole 48,must be reduced to allow more tracks per inch to be written on themedium. Write pole 48 must be fabricated within tight tolerances.Accurately transferring the pattern to the write pole material 80contributes to maintaining write pole 48 within the allotted tolerances.In order to accurately pattern write pole material 80, the hard maskused in the patterning must have a lower mill rate than write polematerial 80 so that the hard mask is not removed during the milling ofwrite pole 48. Further, in order to form a trapezoidal shaped write pole48, which involves a larger mill angle, the hard mask must have a lowermill rate than write pole material 80 at all mill angles. FIG. 8 showsthe mill rates of amorphous carbon (a-C) (used in carbon hard mask 84)and FeCo (used in write pole material 80). Amorphous carbon has a lowermill rate at all angles compared FeCo, allowing carbon hard mask 84formed of a-C to accurately pattern FeCo write pole material 80 duringthe milling process.

FIG. 8 also shows the mill rate of alumina (Al₂O₃). Alumina can be usedas a hard mask in place of carbon hard mask 84. However, at mill rateangles θ_(m) greater than about 55 degrees, alumina has a higher millrate than FeCo. At these large mill angles, portions of an alumina hardmask will be removed faster than the FeCo write pole material. Thischaracteristic of alumina is especially important when fabricatingtrapezoidal write poles, which use larger mill angles. An alumina hardmask will not accurately transfer the desired pattern (i.e. width) toFeCo. The alumina hard mask will also be unable to maintain the width ofthe write pole material at the trailing edge because the hard mask willbe milled away. This causes the sidewalls of the write pole to be lesssteep (the sidewall angle θ_(s) is less so that the sidewalls are morevertical). The use of carbon hard mask 84 improves the accuracy of thepattern transferred to write pole material 80 and results in write pole48 with sidewalls 78 that have a larger sidewall angle θ_(s) and thatare steeper.

Carbon hard mask 84 has many advantages. Carbon hard mask 84 has a highhardness and, as described above, has a higher etch/mill resistance thanother hard mask materials such as alumina. Carbon hard mask 84 is alsochemically inert. Further, carbon hard mask 84 can be patterned byoxygen or hydrogen plasma and can be dry striped under the sameconditions as photoresist 88.

However, carbon hard mask 84 is very sensitive to oxygen, such asoxygen-containing byproducts generated during the ion mill/etchingprocess. FIG. 9 is a cross-section of a write element during the millingprocess and illustrates the effect of oxygen on carbon hard mask 84.During argon milling, energetic AlOx radicals, AlOx+ radicals and O+ions are produced by alumina insulating layer 92. Theseoxygen-containing byproducts interact with carbon hard mask 84 to formCO₂, which is a highly volatile product. The high energy oxygen radicalsand ions increase the mill rate of carbon hard mask 84 so that carbonhard mask 84 will mill at a faster rate than write pole material 80. Ascarbon hard mask 84 is milled away, write pole material 80 at trailingedge 20 is also milled away. This reduces the width of write polematerial 80 at trailing edge 20 and results in write pole 48 havingsidewalls 78 that are less steep (have a smaller sidewall angle θ_(s)).

Other drawbacks of using carbon hard mask 84 with alumina insulatinglayer 92 include direct redeposition of the AlOx radicals producedduring the milling process on carbon hard mask 84, and argon ion inducedmixing/reactions on sidewalls 78. The direct redeposition of the AlOxradicals and the argon ion induced mixing/reactions form an intermixmaterial on sidewall 88 that is soft and that is milled at a faster ratethan carbon hard mask 84. The AlOx radicals and argon ions reduce thewidth of write pole material 80 at trailing edge 20 and result in writepole 48 having sidewalls 78 that are less steep (have a smaller sidewallangle θ_(s)).

By replacing alumina insulating layer 92 with oxygen-free buffer layer72, oxygen derivative byproducts (such as ions and high energy radicals)are minimized or eliminated and the sidewall mill resistivity of carbonhard mask 84 is improved. In one example, oxygen-free buffer layer 72 isformed from non-magnetic refractory metals such as tungsten (W),chromium (Cr), molybdenum (Mo), Vanadium (V), niobium (Nb), tantalum(Ta), hafnium (Hf), zirconium (Zr) and titanium (Ti). Refractory metalsform stable carbides in the presence of carbon. During redeposition andion-induced reactions on sidewalls 78 during the milling of write pole48, the refractory metal of carbon hard mask 84 forms intermediatecarbide surface layers having high mill resistivity (low mill rate). Inanother example, carbon hard mask is formed from non-magnetic, non-oxidenitrides, carbides or borides such as AlN, B₄C, TaC, TiN, TiB₂, WC, HfCand Cr₃C. These are hard materials that form stable redepositintermediate surface layers during the milling process. Oxygen-freebuffer layer 72 does not produce radicals or ions during the millingprocess that adversely affect the mill rate of carbon hard mask 84.

Together oxygen-free buffer layer 72 and carbon hard mask 84 providehigh resolution imaging of write pole material 80. The use ofoxygen-free buffer layer 72 reduces or eliminates “oxygen poisoning” ofcarbon hard mask 84, producing write pole 48 having steeper sidewalls 78because of the low mill rate and improved sidewall mill resistance ofcarbon hard mask 84. Further, the low mill rate and improved sidewallmill resistance of carbon hard mask 84 means that a thinner carbon hardmask 84 can be used while still achieving an accurate patterning ofwrite pole material 80, allowing carbon hard mask 84 to be used attechnology nodes of sub-100 nm and beyond.

EXAMPLE

The present invention is more particularly described in the followingexample that is intended as illustration only, since numerousmodifications and variations within the scope of the present inventionwill be apparent to those skilled in the art.

Two layered substrates, layered substrate A and layered substrate B,were prepared using methods known in the art. Layered substrate A wasformed by depositing the following materials in the order presented on asubstrate: an oxygen-free buffer layer formed of tantalum (Ta), a writepole material formed of FeCo, a CMP etch layer formed of amorphouscarbon, a spacer layer formed of alumina, a carbon hard mask formed ofamorphous carbon, a cap layer formed of SiON and a photoresist. Layeredsubstrate B was formed by depositing the following materials in theorder presented on a substrate: an alumina insulating layer, a writepole material formed of FeCo, a CMP etch layer formed of amorphouscarbon, a spacer layer formed of alumina, a carbon hard mask formed ofamorphous carbon, a cap layer formed of SiON and a photoresist. The onlydifference between layered substrate A and layered substrate B is thatlayered substrate A contains an oxygen-free buffer layer formed of Tawhile layered substrate B contains an alumina insulating layer. Layeredsubstrate A and layered substrate B were processed using the methoddescribed above to form a write pole. After each step, the width of thefeature formed was measured. Table 1 presents the results.

TABLE 1 Layered substrate A Layered substrate B (Ta oxygen-free (aluminabuffer layer) insulating layer) Width of photoresist after 146 nm 156 nmpatterning photoresist Width of cap layer after 119 nm 130 nm patterningcap layer Width of carbon hard mask 149 nm 146 nm after patterningcarbon hard mask Width of carbon hard mask 145 nm 108 nm after argon ionmilling

As shown in Table 1, the widths of the measured features vary onlyslightly between layered substrate A and layered substrate B up untilthe argon ion milling. Before the milling process, the carbon hard maskof layered substrate A had a width of about 149 nm. After the millingprocess, the carbon hard mask on layered substrate A, and thus thetrailing edge of the write pole under the carbon hard mask, had a widthof about 145 nm. The carbon hard mask on layered substrate A experiencedlittle erosion during the argon milling process.

In contrast, the carbon hard mask on layered substrate B experiencedabout 38 nm of erosion of its width. Layered substrate B illustrates theeffects of oxygen poisoning on the carbon hard mask. During the argonetch process, oxygen containing radicals and ions were produced by thealumina insulating layer on layered substrate B. These radicals and ionsincrease the mill rate of the carbon hard mask. As a result, the carbonhard mask on layered substrate B was partially removed during the millprocess, resulting in a narrower carbon hard mask after the millingprocess. The carbon hard mask on layered substrate A experienced littleto no change in width because an oxygen-free buffer layer was used inplace of the alumina insulating layer of layered substrate B. Theoxygen-free buffer layer eliminates not only the source of oxygencontamination but also eliminates possible attacks on the carbon hardmask by ion mill byproducts, such as reactive ions and radicals producedin the milling process.

The width of the carbon hard mask after the milling process can also becompared to the width of the photoresist to determine the accuracy ofthe patterning. For layered substrate A, the width of the carbon hardmask is about 10 angstroms wider than the width of the patternedphotoresist. Therefore, layered substrate A having a Ta oxygen-freebuffer layer has a critical dimension (CD) bias of about 10 angstroms.In comparison, for layered substrate B, the width of the carbon hardmask is about 480 angstroms wider than the width of the patternedphotoresist, and layered substrate B has a CD bias of about 480angstroms. The Ta oxygen-free buffer layer of layered substrate Aproduces a write pole having a smaller CD bias compared to using analumina insulating layer.

Further, the write pole fabricated from layered substrate A had steepersidewalls than the write pole fabricated from layered substrate B. Thewrite pole of layered substrate A had sidewalls having a sidewall angle(or wall angle) greater than about 7°, and more specifically thesidewalls had a wall angle of about 10°. In comparison, the sidewalls ofthe write pole formed from layered substrate B had a wall angle of about7°. The Ta oxygen-free buffer layer eliminated oxygen poisoning of thecarbon hard mask. Thus, the carbon hard mask was able to maintain thewidth of the trailing edge of the write pole while the portion of thewrite pole not covered by the carbon hard mask was milled into atrapezoidal shape. On layered substrate B, oxygen radicals and ionsproduced by the alumina insulating layer during the argon millingincreased the etch rate of the carbon hard mask. This increase in etchrate caused a portion of the carbon hard mask to be removed during themilling process. Thus, the carbon hard mask could not maintain the widthof the trailing edge of the write pole and the angles of the sidewallsof the write pole were less steep.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention. For example, although the present inventionhas been described with reference to argon ion milling, write pole 48can also be formed by a reactive ion beam etch process.

1. A magnetic writer comprising: a write pole having a leading edgeside, a trailing edge side, a first side and a second side; a substrateat the leading edge side of the write pole; and a non-magnetic,oxygen-free buffer material located between the write pole and thesubstrate.
 2. The magnetic writer of claim 1, wherein the non-magnetic,oxygen-free buffer material is selected from the group consisting ofrefractory metals.
 3. The magnetic writer of claim 1, wherein thenon-magnetic, oxygen-free buffer material is selected from the groupconsisting of nitrides, carbides and borides.
 4. The magnetic writer ofclaim 1, wherein the non-magnetic, oxygen-free buffer material isselected from the group consisting of W, Cr, Mo, V, Nb, Ta, Hf, Zr, Ti,AlN, B₄C, TaC, TiN, TiB₂, WC, HfC and Cr₃C.
 5. The magnetic writer ofclaim 1, and further comprising an insulator located at the first sideand the second side of the write pole.
 6. The magnetic writer of theclaim 1, wherein the write pole has a trapezoidal shape at an airbearing surface.
 7. The magnetic writer of claim 1, and furthercomprising a chemical mechanical polishing stop layer on the trailingedge side of the write pole.
 8. A method of forming a magnetic writer,the method comprising: depositing a non-magnetic, oxygen-free buffermaterial on a substrate; depositing a high moment magnetic material onthe non-magnetic, oxygen-free buffer material, the magnetic materialhaving a desired thickness for a write pole; depositing a hard mask onthe magnetic material; forming a photoresist mask on the hard mask, thephotoresist mask generally defining the desired shape of the write pole;patterning the hard mask using the photoresist mask; and forming thewrite pole by removing portions of the magnetic material and using thepatterned hard mask as a pattern.
 9. The method of claim 8, wherein thenon-magnetic, oxygen-free buffer material is selected from the groupconsisting of refractory metals, nitrides, carbides and borides.
 10. Themethod of claim 8, wherein the non-magnetic, oxygen-free buffer materialis selected from the group consisting of W, Cr, Mo, V, Nb, Ta, Hf, Zr,Ti, AlN, B₄C, TaC, TiN, TiB₂, WC, HfC and Cr₃C.
 11. The method of claim8, wherein the non-magnetic, oxygen-free buffer material and magneticmaterial are removed by Ar ion milling.
 12. The method of claim 8, andfurther comprising depositing an insulator on the buffer material afterforming the write pole.
 13. The method of claim 8, wherein the hard maskcomprises amorphous carbon or diamond like carbon.
 14. The method ofclaim 8, wherein depositing the hard mask comprises: depositing a stoplayer on the magnetic material; depositing a spacer layer on the stoplayer; depositing a material comprising amorphous carbon or diamond likecarbon on the spacer layer; and depositing a cap layer on the carbonmaterial.
 15. The method of claim 14, wherein the cap layer is selectedfrom silicon oxinitride, silicon nitride and silicon oxide.
 16. Themethod of claim 14, wherein the cap material is between about 50 and 150nanometers thick.
 17. The method of claim 14, wherein the carbonmaterial is between about 4000 and 6000 angstroms thick.
 18. The methodof claim 14, wherein patterning the hard mask comprises: patterning thecap layer using reactive ion etch using fluorinated chemistry; andpatterning the carbon material using reactive ion etch using oxygenchemistry.
 19. The method of claim 8, wherein forming the write polecomprises removing portions of the magnetic material and the buffermaterial so that the write pole has a trapezoidal shape at an endsurface.
 20. A magnetic writer comprising: a write pole having atrapezoidal shape at an air bearing surface; a substrate; anon-magnetic, oxygen-free buffer material located between the write poleand the substrate; a stop layer on an opposite side of the write pole asthe non-magnetic, oxygen-free buffer material; and an insulatorsurrounding the write pole and the stop layer.
 21. The magnetic writerof claim 20, wherein a width of the write pole is less than about 100nanometers and a wall angle of the write pole is greater than about 7degrees from vertical.